My career goal is to identify molecular events that govern pancreas development and functionality and the genetic components that delineate these events. Ultimately, such findings will contribute to better treatments and prevention of pancreatic disease. My current focus is to dissect the role of basic Helix-Loop-Helix (bHLH) factors in pancreatic endocrine cell development. I am currently characterizing a novel bHLH factor, BETA4, which is expressed during ontogeny of the pancreas. I plan to assess the molecular function of this factor in transcription of pancreatic genes. This will be accomplished via transient transfection assays in mammalian cells in culture. Once target promoters are identified, l will examine the ability of BETA4 to bind to DNA at specific sequences via gel retardation assays and to regulate transcription through promoter deletion analysis. However, to determine the physiological role of this factor, l am generating a loss-of- function mouse mutant. The BETA4 gene will be targeted for disruption in embryonic stem cells. In combination, the beta-galactosidase gene will be "knocked-in" such that it is a direct reflection of BETA4 expression. For this purpose, a targeting construct, 'which contains fragments of genomic DNA derived from the BETA4 locus flanking the beta-galactosidase gene and a selectable antibiotic marker gene, is being engineered. Analysis of the BETA4 knockout mouse will reveal both the precise location of BETA4 expression at the cellular level and the role BETA4 plays in the development or the functionality of the pancreas. The BETA4 knockout will be a mouse model system for the study of aspects of pancreas development and possibly pancreatic disease.